#include<stdio.h>
#include<malloc.h>
#include<stdbool.h>

struct TreeNode 
{
    int val;
    struct TreeNode* left;
    struct TreeNode* right;
};
bool _isSymmetric(struct TreeNode* root1, struct TreeNode* root2)
{
    if (root1 == NULL && root2 == NULL)
    {
        return true;
    }
    if (root1 == NULL || root2 == NULL)
    {
        return false;
    }
    if (root1->val != root2->val)
    {
        return false;
    }
    return _isSymmetric(root1->left, root2->right) && _isSymmetric(root1->right, root2->left);
}

bool isSymmetric(struct TreeNode* root)
{
    if (root == NULL)
    {
        return true;
    }
    return _isSymmetric(root->left, root->right);
}